Starting strip for electric discharge devices



y 1950 E. LEMMERS 2,508,118

STARTING STRIP FOR ELECTRIC DISCHARGE DEVICES Filed March 3, 1948 Invewbor: Eggene Lemmevs Hi5 A t tgrnegl v Patented May 16, 19

STARTING STRIP FOR ELECTRIC DISCHARGE DEVICES Eugene Lemmers, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application March 3, 1948, Serial No. 12,788

6 Claims. (Cl. 17 6122) This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to improvements in starting strips used thereon.

In. the past, in order to facilitate starting of the discharge in an electric discharge device, starting strips were used to distort the electrostatic fields and to neutralize the efiect produced by wall charges on the interior of the gas discharge envelope. Selective adsorption of certain ions or electrons clinging to the walls of the en velope was especially prevalent in devices employing a hot and glowing filamentary electrode. These starting strips were usuall made of materials such as silver, aluminum, or bronze paint which, by rubbing or abrasion-action, wiped or wore off or were destroyed or became non-conductive when exposed to high temperature, for example, that temperature necessary for proper sealing operations.

An object of my invention is to provide new and improved conductive starting strips for controlling electric discharge device operation.

Another object of my invention is to provide a new and improved composition which will adhere firmly to the glass wall of the envelope at temperatures above and below the glass fusion point.

A further object of my invention is to provide a new and improved composition containing an ingredient which will combine with another ingredient therein at a predetermined temperature to inhibit coalescence.

Further features and advantages of my invention will appear from the following detailed description of species thereof.

The drawing is a side elevation, partly in seotion, of a discharge device I comprising an elongated tubular or cylindrical envelope 2 having sealed into the ends thereof lead-in wires 3, 4 and 5, 6 electrically connected to the electrodes, such as thermionic electrodes '1 and 8, respectively. Bases 9 and ID are formed with a pair of contact terminals or pins I I, I2 and 13, I4 respectively, to which the lead-in wires 3, 4 and 5, 6 are respectively connected. Suitable provisions may be made (not shown) which connect the contact terminals or pins to a source of electrical energy for starting and maintaining the gaseous discharge between two electrodes and also for heating the electrodes if necessary, whereby they are brought to a glowing and emitting temperature. The thermionic electrodes 1 and 8 are each herein illustrated as comprising a coil, preferably in the form of a coiled coil of tungsten wire activated with the usual mixture of barium and strontium oxides. The envelope 2 contains an ionizable medium. This ionizable medium may comprise a rare gas like neon, argon or mixtures thereof at a pressure of a. few mm. and a small quantity of mercury which, during operation of the lamp, has a low pressure of the orderof 10 microns. A quantity of mercury,

which may be in excess of that vaporized during operation of the device, is indicated by a drop 15 inside the envelope 2. The device I may be a low pressure positive column lamp of the fluorescent type with an internal coating of a suitable phosphor which, under the influence of an electric discharge through the ionizable medium, produces fluorescence.

On the outside of the envelope 2, directly connected to the lead-in wire 3, and terminating in close proximity to the opposite end of the envelope, I provide a starting strip 16 which, for example, may comprise sections a and b of conductive composition and embodying ingredients which will adhere to the glass and remain porous at temperatures above and below the glass fusion point. Section a of starting strip I4 may comprise a portion thereof extending Over the shoulder and sealing areas of envelope 2, while section b may comprise the remaining portion thereof. Starting strip I6 may be connected to lead-in wire 3 through base 9. Base 9, as disclosed and claimed in patent application Serial No. 733,595 of Eugene Lemmers, filed March 10, 1947, and assigned to the assignee of this application, may comprise a metallic shell I! embodying a flat plastic body portion or disc l8 of a predetermined electrical resistance moulded or formed integral therewith. Disc 18 supports contact terminals or pins H and I2 and serves conjointly as an insulator therefor and as a conductive path of predetermined resistive value for connection of lead-in wire 3 through shell I! to starting strip l6. To prevent any possibility of a base cement l9 breaking this electrical connection, a given per cent of carbon is substituted for the usual filler in the basing cement formula. One example of a conductive basing cement incorporating these characteristics is a mixture containing 15 to 17 per cent of a resin consisting of one part of a commercial plastic moulding compound, four parts resin, and six and one-half parts shellac, and 83 to 85 per cent marble flour filler, of which 8 to 20 per cent of the filler would be graphite flakes.

More particularly, I provide a composition for use with a vitreous envelope which will, after heat treatment at temperatures above the glass fusion point, result in a strongly adherent porous film containing metallic particles evenly distributed throughout. The composition essentially comprises a conductive ingredient comprising a combination or alloy of metals and a bonding agent which may fuse at a temperature below that to which the discharge device is subjected during its manufacture. This starting strip may be either inside or outside the glass receptacle and means may be provided for connecting it to both ends, or it may be desirable to permit the starting strip to float, that is, the starting strip is projected along the length of the discharge device and in close proximity to the ends thereof without connection to any electrode.

The present invention constitutes an improvement in starting strips of the nature disclosed and claimed in patent application Serial No. 660,093 of Jonathan Force, now U. S. Patent 2,491,854, issued December 20, 1949, and Serial No. 674,444 of Eugene Lemmers, which were filed April 6, 1946, and June 5, 1946, respectively, and assigned to the assignee of this application. I provide a starting strip construction and material or composition thereof which has the desirable conducting and wearing qualities, and in which the final state of the material after being applied to the envelope is predetermined or .controlled by the use of a group of two or more metals which. when heated together to a predetermined temperature, form a composition which does not coalesce but remains porous and conductive at high temperatures used during sealing operations performed on a device or lamp during its manufacture.

Generally speaking, I effect these desired results by means of a compound comprising ingredients which, when combined in the right proportions and applied to a glass envelope, adhere to the glass and remain porous and conductive at temperatures above and below the glass fusion point. To accomplish this desired result, I provide two metals, at least one of which will melt when submitted to a predetermined temperature and combine with, or dissolve, part or all of the other metal to form a .composition or alloy. The term alloy here used is taken in its broadest form to mean a substance composed of two or more metals mixed and united to form a non-homogeneous mixture of two or more different kinds of metallic crystals. The combining effect of the two metals restrains coalescence, at this predetermined temperature, of the other ingredients of the composition comprising the starting strip material. For example, this conductive substance may be a paste containing 100 grams of silver oxide, 36 grams of lead borate, 60 grams of chromium powder, mixed together with a, suitable binder such as 90 cubic centimeters of methanol, and 80 cubic centimeters of glycerine. The quantity of chromium powder used may vary from 18 grams to 100 grams and still be usable. The texture of the starting strip becomes progressively coarser as the quantity of chromium powder used therein increases. The silver oxide is used as the ingredient which combines with or dissolves part or all of the chromium powder to form the combination or alloy which restrains coalescence of the starting strip ingredients at the temperatures to which they are exposed during the manufacture of the electric discharge devices. Accordingly, if heat treatment below the glass fusion point is applied to a starting strip made of this compound, the lead borate, as claimed in the patent application Serial No. 660,093 01 Jon- 4 athan Force, frits to the glass envelope and forms a porous body throughout which the reduced metal is distributed. If the temperature, however, is raised above the glass fusion point, the lead borate melts and flows into a glassy nonporous material which fuses to the glass envelope of the electric discharge device. According to the present invention the reduced silver oxide combines with the chromium powder and forms a new composition or alloy which restrains coalescence of the fused silver, thus retaining a conductive path. The conductive path, in the form of this new composition, may be subjected to temperatures above the glass fusion point without destroying the continuity of the starting strip.

Application of this composition to the glass envelope 2 may be perfected either before or after the envelope is coated with phosphor and may be applied in any of the well-known methods, such as painting, squirting the material from nozzle, or applying by means of a thin rubber roller. The viscosity, thickness, or stickiness of the composition may be varied to fit the type of application by means of a suitable diluent, such as methyl alcohol.

If desired, my invention comprising a heat resistant composition may be applied to an electric discharge device as a starting strip only over the sealing and shoulder areas of the discharge device subjected to the sealing fires. The remaining portions of the starting strip may comprise a conventional composition of conductive material; however, I prefer to use for this portion of the starting strip the composition disclosed and claimed in the patent application Serial No. 660,- 093 of Jonathan Force which comprises silver oxide and lead borate.

What I .claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a composition containing a fused vitreous bonding agent and rendered conductive by the distribution therethrough of conductive alloyed particles of silver and an alloying metal which combines with and restrains coalescence of said conductive silver particles the said particles of silver and alloying metal being in physical contact and giving to said starting strip a predetermined electrical resistance.

2. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, .a. plurality of electrodes therein, and a starting strip on the surface of said envelope comprising composition containing a fused vitreous bonding agent and rendered conductive by the distribution therethrough of alloyed particles of silver and chromium in physical contact giving to said starting strip a predetermined electrical resistance.

3. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising a composition containing lead borate and rendered conductive by the distribution therethrough of alloyed particles of silver and chromium in physical contact giving to said starting strip a predetermined electrical resistance.

4. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising at least two portions electrically connected together, one of said portions extending over an end portion of said envelope and comprising a composition containing fused lead borate and rendered conductive by the distribution therethrough of alloyed particles of silver and chromium in physical contact giving to said one portion of the starting strip a predetermined electrical resistance, said second portion extending over the remaining section of said envelope occupied by said starting strip and containing lead hereto and rendered conductive by the distribution therethrough of particles of silver in physical contact giving to said second portion of the starting strip a predetermined electrical resistance.

5. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising the conductive fused residue of a paste comprising lead borate, silver oxide and powdered chromium and containing evenly distributed particles of metallic silver and chromium in physical contact giv- 6 ing to said strip a predetermined electrical resistance.

6. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality of electrodes therein, and a starting strip on the surface of said envelope comprising the conductive fused residue of a paste comprising lead borate, silver oxides and powdered chromium in respective proportions by weight of approximately 36, 100 and 18-100 and containing evenly distributed particles of metallic silver and chromium in physical contact giving to said strip a predetermined electrical resistance.

EUGENE LEMMERS.'

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,922,221 Steenbeck Aug. 15, 1933 2,056,613 Mitchell Oct. 6, 1936 2,094,647 Freitag Oct. 5, 193"! 2.146.579 Inman Feb. 7. 1939 

